scheduler: Update scheduler_set_operation_mode()
scheduler: Be more demanding when cancelling penalties
scheduler: Increase penalty of waiting threads

The fact that thread is waiting doesn't mean that it is nice to the others.
If the thread, indeed, waits for a longer time its penalty will be cancelled
anyway, however if the thread waits for a very short time do not count that
as being nice since lower priority threads didn't have much chance to run.
scheduler: Decide whether to cancel thread penalty